Christian Ewelt

Dr. Christian Ewelt


Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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10 December 2020 in Brain Sciences
Verified
Journal Article
Open access
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SASamer Zawy Alsofy
Samer Zawy Alsofy
ISIoanna Sakellaropoulou
Ioanna Sakellaropoulou
Makoto NakamuraMakoto Nakamura
Makoto Nakamura
CEChristian Ewelt
Christian Ewelt
ASAsem Salma
Asem Salma
RSRalf Stroop
Ralf Stroop
Anterior-communicating artery (ACoA) aneurysms have diverse configurations and anatomical variations. The evaluation and operative treatment of these aneurysms necessitates a perfect surgical strategy based on review of three-dimensional (3D) angioarchitecture using several radiologic imaging methods. We analyzed the influence of 3D virtual reality (VR) reconstructions versus conventional computed tomography angiography (CTA) scans on the identification of vascular anatomy and on surgical planning in patients with unruptured ACoA aneurysms. Medical files were retrospectively analyzed regarding patient- and disease-related data. Preoperative CTA scans were retrospectively reconstructed to 3D-VR images and visualized via VR software to detect the characteristics of unruptured ACoA aneurysms. A questionnaire was used to evaluate the influence of VR on the identification of aneurysm morphology and relevant arterial anatomy and on surgical strategy. Twenty-six patients were included and 520 answer sheets were evaluated. The 3D-VR modality significantly influenced detection of the aneurysm-related vascular structure (p = 0.0001), the recommended head positioning (p = 0.005), and the surgical approach (p = 0.001) in the planning of microsurgical clipping. Thus, reconstruction of conventional preoperative CTA scans into 3D images and the spatial presentation in VR models enabled greater understanding of the anatomy and pathology, provided realistic haptic feedback for aneurysm surgery, and influenced operation planning and strategy.

22 August 2022 in Cancers
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Journal Article
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ASAntonio Santacroce
Antonio Santacroce
CTConstantin Tuleasca
Constantin Tuleasca
RLRoman Liščák
Roman Liščák
EMEnrico Motti
Enrico Motti
CLChrister Lindquist
Christer Lindquist
CEChristian Ewelt
Christian Ewelt
Cavernous sinus meningiomas (CSMs) remain a surgical challenge due to the intimate involvement of their contained nerves and blood vessels. Stereotactic radiosurgery (SRS) is a safe and effective minimally invasive alternative for the treatment of small- to medium-sized CSMs. Objective: To assess the medium- to long-term outcomes of SRS for CSMs with respect to tumour growth, prevention of further neurological deterioration and improvement of existing neurological deficits. This multicentric study included data from 15 European institutions. We performed a retrospective observational analysis of 1222 consecutive patients harbouring 1272 benign CSMs. All were treated with Gamma Knife stereotactic radiosurgery (SRS). Clinical and imaging data were retrieved from each centre and entered into a common database. All tumours with imaging follow-up of less than 24 months were excluded. Detailed results from 945 meningiomas (86%) were then analysed. Clinical neurological outcomes were available for 1042 patients (85%). Median imaging follow-up was 67 months (mean 73.4, range 24–233). Median tumour volume was 6.2 cc (+/−7), and the median marginal dose was 14 Gy (+/−3). The post-treatment tumour volume decreased in 549 (58.1%), remained stable in 336 (35.6%) and increased in only 60 lesions (6.3%), yielding a local tumour control rate of 93.7%. Only 27 (2.8%) of the 60 enlarging tumours required further treatment. Five- and ten-year actuarial progression-free survival (PFS) rates were 96.7% and 90.1%, respectively. Tumour control rates were higher for women than men (p = 0.0031), and also for solitary sporadic meningiomas (p = 0.0201). There was no statistically significant difference in outcome for imaging-defined meningiomas when compared with histologically proven WHO Grade-I meningiomas (p = 0.1212). Median clinical follow up was 61 months (mean 64, range 6–233). Permanent morbidity occurred in 5.9% of cases at last follow-up. Stereotactic radiosurgery is a safe and effective method for treating benign CSM in the medium term to long term.

30 January 2024 in Journal of Clinical Medicine
Verified
Journal Article
Open access
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SASamer Zawy Alsofy
Samer Zawy Alsofy
MLMarc Lewitz
Marc Lewitz
KMKyra Meyer
Kyra Meyer
TFThomas Fortmann
Thomas Fortmann
EWEike Wilbers
Eike Wilbers
CEChristian Ewelt
Christian Ewelt
(1) Background: In this study, epidemiological, clinical, therapeutical, and haemostaseological variables were investigated regarding their correlation with the recurrence of chronic subdural haematomas to assess the risk of recurrence more reliably in everyday clinical practice. (2) Methods: In our retrospective study, the electronic records of 90 patients who underwent surgery for a chronic subdural haematoma at our institute between 1 January 2017 and 31 May 2021 were analysed regarding previously defined variables. (3) Results: In the patient collective, 33.33% of the 90 patients experienced a recurrence requiring treatment. The occurrence of a recurrence was not statistically significantly related to age, gender, known alcohol abuse, a specific location, extension over one or both hemispheres, the surgical method, or anticoagulant medication. However, the recurrence was statistically significantly related to haematoma width (p = 0.000007), septation (p = 0.005), and the existence of a coagulation disorder not treated with medication (p = 0.04). (4) Conclusions: In our study, the width of the haematoma, septation, and coagulation disorders not treated with medication were documented as risk factors for the occurrence of a chronic subdural haematoma. Identifying of these risk factors could help in adapting individual therapeutic concepts for chronic subdural haematomas.

17 June 2024 in Cancers
Verified
Journal Article
Open access
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HSHraq Sarkis
Hraq Sarkis
SASamer Zawy Alsofy
Samer Zawy Alsofy
RSRalf Stroop
Ralf Stroop
MLMarc Lewitz
Marc Lewitz
SSStephanie Schipmann
Stephanie Schipmann
CEChristian Ewelt
Christian Ewelt
(1) Background: In this study, the intraoperative fluorescence behavior of brain metastases after the administration of 5-aminolevulinic acid (5-ALA) was analyzed. The aim was to investigate whether the resection of brain metastases using 5-ALA fluorescence also leads to a more complete resections and thus to a prolongation of survival; (2) Methods: The following variables have been considered: age, sex, number of metastases, localization, involvement of eloquent area, correlation between fluorescence and primary tumor/subtype, resection, and survival time. The influence on the degree of resection was determined with a control MRI within the first three postoperative days; (3) Results: Brain metastases fluoresced in 57.5% of cases. The highest fluorescence rates of 73.3% were found in breast carcinoma metastases and the histologic subtype adenocarcinoma (68.1%). No correlation between fluorescence behavior and localization, primary tumor, or histological subtype was found. Complete resection was detected in 82.5%, of which 56.1% were fluorescence positive. There was a trend towards improved resectability (increase of 12.1%) and a significantly longer survival time (p = 0.009) in the fluorescence-positive group; (4) Conclusions: 5-ALA-assisted extirpation leads to a more complete resection and longer survival and can therefore represent a low-risk addition to modern surgery for brain metastases.

14 January 2026 in Journal of Clinical Medicine
Verified
Journal Article
Open access
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TFThomas Fortmann
Thomas Fortmann
SASamer Zawy Alsofy
Samer Zawy Alsofy
ASAntonio Santacroce
Antonio Santacroce
Makoto NakamuraMakoto Nakamura
Makoto Nakamura
CEChristian Ewelt
Christian Ewelt
RLRalph Edmund Lehrke
Ralph Edmund Lehrke
Background/Objectives: Patients with deep brain stimulation (DBS) require regular follow-up. When a sudden loss of therapeutic effect occurs, impedance abnormalities are often the underlying cause. If reprogramming cannot restore clinical benefit, revision surgery may be necessary to replace defective hardware. Since all three major manufacturers are used at our center, we analyzed our patient cohort to determine the incidence and causes of impedance abnormalities. Methods: All 601 patients who underwent de novo DBS implantation in Hamm between 2009 and 2025 were evaluated for impedance abnormalities. In cases requiring revision surgery, the specific cause was identified. The manufacturer, electrodes, and contacts involved were systematically analyzed. Results: A total of 25 of 601 patients required revision surgery. Revision rates were 2.67% in patients with Parkinson’s disease, 6.19% in those with a tremor, and 5.71% in those with dystonia. Across manufacturers, 7.6% of patients with a Medtronic system required revision surgery, compared with 3.4% of patients with an Abbott system and no patients with a Boston Scientific system. The primary causes of revision were electrode-related problems (19/25), followed by extension defects (6/25), connector issues (4/25), and, in one case, a generator defect (1/25). Conclusions: Only 4.16% of patients required revision surgery due to impedance abnormalities. Patients with a tremor and non-segmented electrodes showed a higher incidence than those with Parkinson’s disease or dystonia. Predominantly older Medtronic systems had the highest revision rate, whereas no Boston Scientific systems required revision. In most cases, the electrodes were the primary source of impedance abnormalities. A total of 52% of revisions were performed within two years and 92% were performed within six years of implantation.

5 February 2025 in Medicina
Verified
Journal Article
Open access
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JBJan-Niklas Becker
Jan-Niklas Becker
MFMirko Fischer
Mirko Fischer
HCHans Christiansen
Hans Christiansen
MSMichael Schwake
Michael Schwake
WSWalter Stummer
Walter Stummer
Michael MütherMichael Müther
Michael Müther
Background and Objectives: The utilization of non-metallic pedicle screws and rods has become a favored approach in the management of spinal tumors. An abundance of metal artifacts improves postoperative imaging and allows for precise radiation treatment planning. Under certain conditions, a vertebral body replacement (VBR) is necessary in addition to dorsal fixation. For a long time, VBR hardware was available as titanium implants only. Recently, other non-titanium products were introduced into the market. This study compares radiotherapy planning after VBR with titanium and non-titanium materials. Materials and Methods: This is a retrospective cohort study in a single academic center setting. VBR was performed for thoracic spinal metastatic disease. Radiation plan quality was evaluated according to the criteria of the International Commission on Radiation Units and Measurements, based on postoperative CT imaging. Results: Six patients with dorsal fixation and VBR were included, half of which were treated with titanium VBR and the other half with a minimum metallic implant. In addition, patients received different dorsal fixation hardware. No difference was found in terms of radiation plan quality. With non-titanium materials, visual demarcation during radiation planning was superior. Conclusions: This is the first study in the field to comprehensively compare radiation treatment planning after VBR using different materials. With minimum metallic implants, radiotherapy planning is equal in terms of planning but superior in terms of visual demarcation in comparison to standard titanium VBR, potentially enabling more precise radiotherapy approaches.